Requirements and Use Cases Modelling Class T04 Requirements and Use Cases References: http://www.sysml.org http://www.omg.org

UML and SysML Modelação

UML – An overview… Modelação

SysML – An overview… Modelação

A Context Diagram (example for a HybridSUV system) Modelação

Use Cases Use cases describes an interaction between the system and other external entity (an actor). The description must be provided from the point of view of the actor! Therefore it describes "who" can do or is affected by "what" with or from the system. The use case technique is used to elicit functional requirements by relating them with usage/behavioral scenarios. In a document requirements the use cases can be presented before the lists of requirements, as they can provide good glimpses… Use cases are also useful to make the bridge between the requirements documenting and the modeling of the detailed systems’ behavior Modelação

High level use cases Modelação

High level use cases Use Cases Actors Modelação

High level use cases These actors might be the same object, but conceptually we must consider them independents Modelação

Casos de Uso: Example of a template Name UC-8: Search Summary All occurrences of a search term are replaced with replacement text. Rationale While editing a document, many users find that there is text somewhere in the file being edited that needs to be replaced, but searching for it manually by looking through the entire document is time-consuming and ineffective. The search-and-replace function allows the user to find it automatically and replace it with specified text. Sometimes this term is repeated in many places and needs to be replaced. Other times, only the first occurrence should be replaced. The user may also wish to simply find the location of that text without replacing it. Users All users Preconditions A document is loaded and being edited. Basic Course of Events The user indicates that the software is to perform a search-and-replace in the document. The software responds by requesting the search term and the replacement text. The user inputs the search term and replacement text and indicates that all occurrences are to be replaced. The software replaces all occurrences of the search term with the replacement text. Alternative Paths In step 3, the user indicates that only the first occurrence is to be replaced. In this case, the software finds the first occurrence of the search term in the document being edited and replaces it with the replacement text. The postcondition state is identical, except only the first occurrence is replaced, and the replacement text is highlighted. In step 3, the user indicates that the software is only to search and not replace, and does not specify replacement text. In this case, the software highlights the first occurrence of the search term and the use case ends. The user may decide to abort the search-and-replace operation at any time during steps 1, 2 or 3. In this case, the software returns to the precondition state. Postconditions All occurrences of the search term have been replaced with the replacement text. Modelação

Driver’s use cases Modelação

Driver’s use cases Modelação

Driver’s use cases Complex use cases can be detailed in other diagrams… Modelação

SysML – An overview… Modelação

Requirements and Stakeholders A requirement specifies a capability or condition that must (or should) be satisfied.. A requirement may specify a function that a system must perform or a performance condition that a system must satisfy. Requirements are used to establish a contract between the customer (or other stakeholder) and those responsible for designing and implementing the system. Stakeholders Anybody involved in the system’s lifecycle (analysis, design, development, maintenance, …) Anybody else who, directly or indirectly, may impose requirements for the system (business owner, user, …) Modelação

Types of requirements Functional Requirements (FR) The specification of a function of the system or its components. It must refer a behaviour of the system! Non-Functional Requirements (NFR) It must refer how the system must behave. Examples of non-functional requirements: Performance; Scalability; Availability; Reliability; Maintainability; Serviceability; Security; Regulatory; Manageability; Usability; Interoperability Modelação

Requirements specification Modelação

Requirements derivation Modelação

Requirements in the Enterprise Architect… VERY IMPORTANT: Be aware that EA tool supports requirements diagrams as formal SysML Requirements Diagrams or as informal requirements diagrams as extensions to UML Modelação

Requirements containment The containment (cross hair) relationship refers to the practice of decomposing a complex requirement into simpler, single requirements. Modelação

Copy relationship A Copy relationship is a dependency between a supplier requirement and a client requirement that specifies that the text of the client requirement is a read-only copy of the text of the supplier requirement. A Copy dependency created between two requirements maintains a master/slave relationship between the two elements for the purpose of requirements re-use in different contexts. When a Copy dependency exists between two requirements, the requirement text of the client requirement is a read-only copy of the requirement text of the requirement at the supplier end of the dependency. Modelação

Callout relationship (notes) A callout notation can be used to represent derive, satisfy, verify, refine, copy, and trace relationships… Modelação

DeriveReqt relationship A DeriveReqt relationship is a dependency between two requirements in which a client requirement can be derived from the supplier requirement. For example, a system requirement may be derived from a business need, or lower-level requirements may be derived from a system requirement. As with other dependencies, the arrow direction points from the derived (client) requirement to the (supplier) requirement from which it is derived. Modelação

Verify relationship A Verify relationship is a dependency between a requirement and a test case or other model element that can determine whether a system fulfills the requirement. Modelação

Satisfy relationship A Satisfy relationship is a dependency between a requirement and a model element that fulfills the requirement. Modelação

Refine relationship The refine requirement relationship can be used to describe how a model element or set of elements can be used to further refine a requirement. For example, a use case or activity diagram may be used to refine a text-based functional requirement. Alternatively, it may be used to show how a text-based requirement refines a model element. In this case, some elaborated text could be used to refine a less fine-grained model element Modelação

Trace relationship A generic trace requirement relationship provides a general-purpose relationship between a requirement and any other model element. The semantics of trace include no real constraints and therefore are quite weak. As a result, it is recommended that the trace relationship not be used in conjunction with the other requirements relationship... Modelação

Relating requirements with other elements Modelação

Use Cases Modelação

Use cases and requirements Modelação

Traceability in the Enterprise Architect tool A fundamental technique in modelling to relate decisions with their origin or implications Traceability in the Enterprise Architect tool Traceability Diagrams Relationship Matrix Modelação